Seminars

Lecturer: Rickard Lundin (IRF)
Date: 2016-04-14 11:20
Place: Aniara

On the abundance of deuterium in celestial objects

Rickard Lundin, Johan Kero, Ludwig Liszka
Swedish Institute of Space Physics

The deuterium hydrogen ratio (D/H) is the subject of conflicting ideas about the origin of water on the Earth. The present D/H ratio in the Earth oceans (≈1.5x10-4) is substantially lower than most, if not all potential cosmic sources. Furthermore, other celestial bodies, including interstellar space, display a fairly wide range of D/H ratios superseding the terrestrial one. Escape processes may in part explain higher D/H ratios on Mars and Venus, but cannot explain the Earth's low ratio compared to that of the potential sources (e.g. comets and meteors), unless a deuterium "removal" process can be inferred that reduces the D/H ratio. Alternatively, the D/H ratio in the Earth's ocean represents a time capsule of a yet to be identified cosmic source.
It is here hypothesized that the former is the cause, a "removal" of deuterium in matter (carbohydrates, water etc.) having high (pristine) D/H ratios. By "removal" is here meant an isotope transmutation, i.e. deuterium is transmuted to hydrogen plus a thermal neutron, a process requiring >2.25 MeV (≈3.6·10-13 J). However, once released a thermal neutron will fuse with another heavier element by thermal neutron capture, a process that may lead to energy in excess of the spallation energy. The energy gain differs for different isotopes, but if exceeding unity it will induce more heat/power than the input power, maintaining power production over time. A gain less than unity will still result in deuterium removal, but also isotope transmutation, and/or element transmutation via beta± decay.
This report gives a theoretical background for the plasma forcing that can lead to thermal neutron spallation, a process that changes/decrease the D/H ratio in celestial objects. The applicability of the theory can be tested on celestial objects subjected to strong dynamic, and electromagnetic forcing. For instance the forcing induced by high-speed entries of celestial objects into the Earth's atmosphere, as exemplified by the February 15 2013 Chelyabinsk meteor airburst.


Created 2016-04-01 11:16:16 by Mats Holmström
Last changed 2016-04-07 11:14:58 by Mats Holmström